Among industrial machines and construction machines, there are machines in Which a hydraulic drive system including a variable displacement pump is installed. For example, Patent Literature 1 discloses a load-sensing hydraulic drive system.
Specifically, the hydraulic drive system includes: a variable displacement pump; a control valve that controls supply and discharge of a hydraulic oil to and from an actuator; and an operating device including an operating lever, the operating device moving the control valve. The discharge flow rate of the pump is controlled by a flow regulator, such that the differential pressure between the discharge pressure of the pump and the load pressure of the actuator is constant.